Many types of polymers may be recycled or their chemical values recovered by various means. Polyesters of various types have been hydrolyzed or reacted with alcohols to recover the various chemical units present in the polymers. The recovered compounds are then reused, often in the formation of new polyester polymer. However in order to use a compound as a monomer in a condensation polymerization, it is well known that the compound should be pure and especially be free of various types of impurities that may interfere with a commercial scale polymerization, which should be routinely reproducible. Thus especially when recycling relatively clean scrap polymer, the recycling process should preferably be simple and yield products which are pure.
U.S. Pat. No. 5,473,102 describes the hydrolysis of polymers containing various aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and 2,6-naphthalene dicarboxylic acid (N) by hydrolysis and subsequent distillation of the hydrolysis products by codistillation with steam. The hydrolysis of N containing polyesters in the presence of a carboxylic acid is not described.
U.S. Pat. No. 3,629,202 describes the treatment of polyesters with various carboxylic acids to make them resistant to hydrolysis.
H. Zhang, et al., Macromolecules, vol. 28, p. 7622-7629 (1995) describe the kinetics of the hydrolysis of poly(ethylene 2,6-naphthalate) (PEN). The presence of added carboxylic acids for the hydrolysis is not mentioned.